Is my fiber cement installed correctly?

Answered by Jeffrey Anderson ~ April 12, 2013 ~ No Comments

I had some fiber cement board put on a sloped gable above my garage. The contractor left about an inch of flashing exposed to the side of the trim board. He said it provided better drainage than if the trim board was on top of the shingles. Won't water flow under the shingles where the gap is??

Dave -- Indianapolis, IN

Jeffrey Anderson

Dave, I'm having a difficult time visualizing what you feel may be a problem area on your garage. I understand the part about the sloped gable and the fiber cement trim board, but am not quite sure where the gap is located. If the trim board is running down the rake created by the roof pitch, it should be up tight against the underside of the shingle overlap. There might be a slight space between the shingles and fiber cement that would allow you to see drip edge or flashing, but it shouldn't be more than about ¼ inch.

I do agree with the contractor that the trim board should not cover any of the shingles as that could affect roof drainage. If the gap is at the ends of the fiber cement trim board, it could be to permit expansion during temperature changes. However, even then it should be very small and barely noticeable.

If the roofing has been done correctly and there haven't been any water intrusion problems in the past, I don't believe the location of the trim board should cause any future leakage issues. It sounds like the gap might be just a cosmetic concern. That being said, depending on its size and location, I understand how it could be detracting from the appearance of your home.

Since the original contractor feels it has been done correctly, the best option at this point might be to get a third party involved. While municipal building inspectors normally don't get involved in cosmetic issues, it might be worth a call to see if one of your local officials could take a look at the fiber cement trim board installation. It wouldn't cost you anything and shouldn't take much of their time … especially if you can wait until they're in your area.

If that isn't possible, asking another contractor or an independent inspector to take a look might be the next best option. They may charge a little for their visit, but at least you'll know whether the original installation was done correctly.

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